1. Field
Embodiments of the present disclosure relate to an induction heating cooker capable of heating a vessel that is disposed at any place on a cooking plate.
2. Description of the Related Art
In general, an induction heating cooker is an apparatus configured to cooking foods by supplying a high frequency current to a heating coil to generate a high frequency magnetic field and by causing eddy currents in a cooking vessel (hereinafter referred to as a vessel) having a magnetic coupling with the cooking coil through the generated magnetic field such that the vessel is heated by Joule's heat generated through the eddy current to cook foods.
Inside a body, which forms an external appearance of an induction heating cooker, is fixedly provided with a plurality of heating coils to provide heat source. In addition, a cooking plate is provided on the body to place a vessel. A vessel line is engraved on a predetermined position of a cooking plate corresponding to a heating coil. The vessel line serves to indicate a position where a vessel is to be placed when a user cooks foods.
However, in order to cook food, that is, heating a vessel for foods by use of such as conventional induction heating cooker, a user needs to place the vessel exactly on the vessel line of the cooking plate, causing inconvenience to the user. If a user places on an area deviated from the vessel line, the cooking is not appropriately performed.
According to an induction heating cooker, which is developed as an effort to improve shortcomings associated with such a limited cooking region, has a plurality of heating coils disposed under the entire surface of a cooking plate, such that the cooking is performed regardless of the position of the cooking plate where a vessel is placed.
In order to supply a high frequency current to the plurality of heating coils in the induction heating cooker, a plurality of inverter circuits need to be provided corresponding to the number of the heating coils. The inverter circuits are placed on a printed circuit board (PCB) together with a subsidiary control unit (sub-microcomputer) that is configured to control the operation of each heating coil according to a control signal of a main control unit (main-microcomputer).
On the printed circuit board provided on the induction heating cooker, a circuit part characterized by high voltage/high frequency is not separately disposed from a circuit part characterized by low voltage/low frequency. In addition, a wire connected to a respective inverter circuit is connected to a respective heating coil. Accordingly, interference occurs between the wire, which is characterized by high frequency, and the subsidiary control unit, which is characterized by low frequency, and thus an output waveform of the subsidiary control unit is distorted and a communication error occurs between the main control unit and the subsidiary control unit, failing to operate each heating coil properly. In addition, the induction heating cooker has a connection structure in which a wire withdrawn from an inverter circuit is connected to a heating coil corresponding to the inverter circuit, thereby degrading assembly efficiency and work efficiency in wiring the heating coil with each of the corresponding inverter circuit.
In addition, the induction heating cooker has a structure, including a plurality of small heating coils, densely disposed under the cooking plate over the entire surface, and requires increased number of heating coils; and also increases the number of inverter circuits required.
In this case, increased number of inverter circuits need to be placed on a limited area of the PCB, thereby causing the PCB to have a very complicated circuit structure. Such a complicated circuit structure increases the signal waveform distortion caused by the interference between the high frequency circuit part and the low frequency circuit part on the PCB.
In addition, in order to cook food by use of the induction heating cooker, a user needs to place a vessel on a cooking plate and perform a vessel position detection operation to detect the position of the heating coil where the vessel is placed before the cooking is performed. Thereafter, the induction heating cooker performs the cooking by only operating a heating coil where the vessel is placed, according to the vessel position detection operation.
If a vessel placed on a heating coil occupies a critical percentage (40%, for example) of the area of the heating coil, that is, the occupancy ratio of a vessel (P) on a heating coil (L) (hereinafter referred to as a vessel occupancy ratio) exceeds a critical percentage of the area of the heating coil (L), the heating coil (L) is determined as a heating coil (L) having a vessel (P) placed thereon and is operated for cooking food. Meanwhile, if a vessel (P) is not placed on a heating coil (L), or even if a vessel (P) is placed on a heating coil (L) while the vessel (P) occupies an area of the heating coil (L) below a critical percentage (40%, for example), the heating coil (L) is determined as a heating coil which does not have a vessel (P) placed thereon and thus the heating coil (P) is not operated.
In general, a heating coil of an induction heating cooker is provided in a circular shape according to the shape of a vessel and the working efficiency of a coil wiring process. Alternatively, a heating coil of an induction heating cooker may be provided in an elliptical shape or a triangular shape according to the characteristics of the induction heating cooker.
If a plurality of heating coils having a circular shape (or an elliptical shape) are densely disposed over the entire surface of the cooking plate, a dead zone is formed between the heating coils. In this case, if a user performs cooking by use of a small vessel having a small bottom, the cooking may not be performed depending on the position where the small vessel is placed. That is, if a vessel having a small bottom area occupies a critical percentage of the area of a heating coil, the heating coil is determined as a heating coil where a vessel is placed and the heating coil is operated to cook food. In this case, one or more heating coils may be operated based on the vessel position detecting operation. If at least one part of the bottom of a vessel is placed on a dead zone between heating coils, the vessel may fail to occupy a critical percentage of the area of a heating coil, or may occupy only an area of the heating coil below a critical percentage as heating coil is determined as a heating coil that does not have a vessel placed thereon; that is, it is determined that a vessel is not placed on a cooking plate. Accordingly, the heating coil is not operated, and although a vessel is placed on a cooking plate, a cooking is not performed.